Effect of Low-pressure Pulmonary Recruitment Maneuver on Postlaparoscopic Shoulder Pain: Randomized Controlled Trial.

STUDY OBJECTIVE: Postlaparoscopic shoulder pain (PLSP) is effectively reduced by a pulmonary recruitment maneuver (PRM). The goal of this study is to assess the efficacy of a PRM using maximal inspiratory pressure of 30 cm H2O, which is lower than previously studied pressure for reducing PLSP. DESIGN: Randomized controlled trial. SETTING: University hospital. PATIENTS: Eighty-four patients who were undergoing elective gynecologic laparoscopy. INTERVENTIONS: Patients were randomly assigned to the control (n = 42) or the PRM (n = 42) group. MEASUREMENTS AND MAIN RESULTS: The primary outcome was the intensity of the shoulder pain using the visual analog scale (VAS). The VAS score of shoulder pain (median [interquartile range]) was significantly lower in the PRM group than in the control group at 24 hours (0 [0-0] vs 1.5 [0-4.0], p <.001) and 48 hours (0 [0-0] vs 1.0 [0-2.0], p <.001) after surgery. Other variables, including surgical pain score and vital signs, were similar between the 2 groups. CONCLUSION: The PRM with 30 cm H2O can be a simple method to reduce PLSP. Therefore, it would be helpful to perform the PRM with 30 cm H2O routinely.

Comparison of Carbon Dioxide Absorption Rates in Gynecologic Laparoscopy with a Valveless versus Standard Insufflation System: Randomized Controlled Trial.

STUDY OBJECTIVE: The primary objective was to compare carbon dioxide (CO2) absorption rates in patients undergoing gynecologic laparoscopy with a standard versus valveless insufflation system (AirSeal; ConMed, Utica, NY) at intra-abdominal pressures (IAPs) of 10 and 15 mm Hg. Secondary objectives were assessment of surgeons' visualization of the operative field, anesthesiologists' ability to maintain adequate end-tidal CO2 (etCO2), and patients' report of postoperative shoulder pain. DESIGN: A randomized controlled trial using an equal allocation ratio into 4 arms: standard insufflation/IAP 10 mm Hg, standard insufflation/IAP 15 mm Hg, valveless insufflation/IAP 10 mm Hg, and valveless insufflation/IAP 15 mm Hg. SETTING: Single tertiary care academic institution. PATIENTS: Women ≥ 18 years old undergoing nonemergent conventional or robotic gynecologic laparoscopic surgery. INTERVENTIONS: A standard or valveless insufflation system at IAPs of 10 or 15 mm Hg. MEASUREMENTS AND MAIN RESULTS: One hundred thirty-two patients were enrolled and randomized with 33 patients per group. There were 84 robotic cases and 47 conventional laparoscopic cases. CO2 absorption rates (mL/kg*min) did not differ across groups with mean rates of 4.00 ± 1.3 in the valveless insufflation groups and 4.00 ± 1.1 in the standard insufflation groups. The surgeons' rating of overall visualization of the operative field on a 10-point Likert scale favored the valveless insufflation system (median visualization, 9.0 ± 2.0 cm and 9.5 ± 1.8 cm at 10 and 15 mm Hg, respectively) over standard insufflation (7.0 ± 3.0 cm and 7.0 ± 2.0 cm at 10 and 15 mm Hg, respectively; p <.001). The anesthesiologists' ability to maintain adequate etCO2 was similar across groups (p = .417). Postoperative shoulder pain scores were low overall with no significant difference across groups (p >.05). CONCLUSION: CO2 absorption rates, anesthesiologists' ability to maintain adequate etCO2, and postoperative shoulder pain did not differ based on insufflation system type or IAP. Surgeons' rating of visualization of the operative field was significantly improved when using the valveless over the standard insufflation system.

Expression of the human isoform of glutamate dehydrogenase, hGDH2, augments TCA cycle capacity and oxidative metabolism of glutamate during glucose deprivation in astrocytes.

A key enzyme in brain glutamate homeostasis is glutamate dehydrogenase (GDH) which links carbohydrate and amino acid metabolism mediating glutamate degradation to CO2 and expanding tricarboxylic acid (TCA) cycle capacity with intermediates, i.e. anaplerosis. Humans express two GDH isoforms, GDH1 and 2, whereas most other mammals express only GDH1. hGDH1 is widely expressed in human brain while hGDH2 is confined to astrocytes. The two isoforms display different enzymatic properties and the nature of these supports that hGDH2 expression in astrocytes potentially increases glutamate oxidation and supports the TCA cycle during energy-demanding processes such as high intensity glutamatergic signaling. However, little is known about how expression of hGDH2 affects the handling of glutamate and TCA cycle metabolism in astrocytes. Therefore, we cultured astrocytes from cerebral cortical tissue of hGDH2-expressing transgenic mice. We measured glutamate uptake and metabolism using [3 H]glutamate, while the effect on metabolic pathways of glutamate and glucose was evaluated by use of 13 C and 14 C substrates and analysis by mass spectrometry and determination of radioactively labeled metabolites including CO2 , respectively. We conclude that hGDH2 expression increases capacity for uptake and oxidative metabolism of glutamate, particularly during increased workload and aglycemia. Additionally, hGDH2 expression increased utilization of branched-chain amino acids (BCAA) during aglycemia and caused a general decrease in oxidative glucose metabolism. We speculate, that expression of hGDH2 allows astrocytes to spare glucose and utilize BCAAs during substrate shortages. These findings support the proposed role of hGDH2 in astrocytes as an important fail-safe during situations of intense glutamatergic activity. GLIA 2017;65:474-488.

Capnography in the Emergency Department: A Review of Uses, Waveforms, and Limitations.

BACKGROUND: Capnography has many uses in the emergency department (ED) and critical care setting, most commonly cardiac arrest and procedural sedation. OBJECTIVE OF THE REVIEW: This review evaluates several indications concerning capnography beyond cardiac arrest and procedural sedation in the ED, as well as limitations and specific waveforms. DISCUSSION: Capnography includes the noninvasive measurement of CO2, providing information on ventilation, perfusion, and metabolism in intubated and spontaneously breathing patients. Since the 1990s, capnography has been utilized extensively for cardiac arrest and procedural sedation. Qualitative capnography includes a colorimetric device, changing color on the amount of CO2 present. Quantitative capnography provides a numeric value (end-tidal CO2), and capnography most commonly includes a waveform as a function of time. Conditions in which capnography is informative include cardiac arrest, procedural sedation, mechanically ventilated patients, and patients with metabolic acidemia. Patients with seizure, trauma, and respiratory conditions, such as pulmonary embolism and obstructive airway disease, can benefit from capnography, but further study is needed. Limitations include use of capnography in conditions with mixed pathophysiology, patients with low tidal volumes, and equipment malfunction. Capnography should be used in conjunction with clinical assessment. CONCLUSIONS: Capnography demonstrates benefit in cardiac arrest, procedural sedation, mechanically ventilated patients, and patients with metabolic acidemia. Further study is required in patients with seizure, trauma, and respiratory conditions. It should only be used in conjunction with other patient factors and clinical assessment.

Quantitative mapping of cerebrovascular reactivity using resting-state BOLD fMRI: Validation in healthy adults.

In conventional neuroimaging, cerebrovascular reactivity (CVR) is quantified primarily using the blood-oxygenation level-dependent (BOLD) functional MRI (fMRI) signal, specifically, as the BOLD response to intravascular carbon dioxide (CO2) modulations, in units of [%ΔBOLD/mmHg]. While this method has achieved wide appeal and clinical translation, the tolerability of CO2-related tasks amongst patients and the elderly remains a challenge in more routine and large-scale applications. In this work, we propose an improved method to quantify CVR by exploiting intrinsic fluctuations in CO2 and corresponding changes in the resting-state BOLD signal (rs-qCVR). Our rs-qCVR approach requires simultaneous monitoring of PETCO2, cardiac pulsation and respiratory volume. In 16 healthy adults, we compare our quantitative CVR estimation technique to the prospective CO2-targeting based CVR quantification approach (qCVR, the "standard"). We also compare our rs-CVR to non-quantitative alternatives including the resting-state fluctuation amplitude (RSFA), amplitude of low-frequency fluctuation (ALFF) and global-signal regression. When all subjects were pooled, only RSFA and ALFF were significantly associated with qCVR. However, for characterizing regional CVR variations within each subject, only the PETCO2-based rs-qCVR measure is strongly associated with standard qCVR in 100% of the subjects (p≤0.1). In contrast, for the more qualitative CVR measures, significant within-subject association with qCVR was only achieved in 50-70% of the subjects. Our work establishes the feasibility of extracting quantitative CVR maps using rs-fMRI, opening the possibility of mapping functional connectivity and qCVR simultaneously.

Simultaneous multi-slice (SMS) acquisition enhances the sensitivity of hemodynamic mapping using gas challenges.

Hemodynamic mapping using gas inhalation has received increasing interest in recent years. Cerebrovascular reactivity (CVR), which reflects the ability of the brain vasculature to dilate in response to a vasoactive stimulus, can be measured by CO2 inhalation with continuous acquisition of blood oxygen level-dependent (BOLD) magnetic resonance images. Cerebral blood volume (CBV) can be measured by O2 inhalation. These hemodynamic mapping methods are appealing because of their absence of gadolinium contrast agent, their ability to assess both baseline perfusion and vascular reserve, and their utility in calibrating the functional magnetic resonance imaging (fMRI) signal. However, like other functional and physiological indices, a major drawback of these measurements is their poor sensitivity and reliability. Simultaneous multi-slice echo planar imaging (SMS EPI) is a fast imaging technology that allows the excitation and acquisition of multiple two-dimensional slices simultaneously, and has been shown to enhance the sensitivity of several MRI applications. To our knowledge, the benefit of SMS in gas inhalation imaging has not been investigated. In this work, we compared the sensitivity of CO2 and O2 inhalation data collected using SMS factor 2 (SMS2) and SMS factor 3 (SMS3) with those collected using conventional EPI (SMS1). We showed that the sensitivity of SMS scans was significantly (p = 0.01) higher than that of conventional EPI, although no difference was found between SMS2 and SMS3 (p = 0.3). On a voxel-wise level, approximately 20-30% of voxels in the brain showed a significant enhancement in sensitivity when using SMS compared with conventional EPI, with other voxels showing an increase, but not reaching statistical significance. When using SMS, the scan duration can be reduced by half, whilst maintaining the sensitivity of conventional EPI. The availability of a sensitive acquisition technique can further enhance the potential of gas inhalation MRI in clinical applications.

Evaluation of renal oxygenation change under the influence of carbogen breathing using a dynamic R2 , R2 ' and R2 * quantification approach.

The purpose of this study is to demonstrate the feasibility of dynamic renal R2 /R2 '/R2 * measurements based on a method, denoted psMASE-ME, in which a periodic 180° pulse-shifting multi-echo asymmetric spin echo (psMASE) sequence, combined with a moving estimation (ME) strategy, is adopted. Following approval by the institutional animal care and use committee, a block design of respiratory challenge with interleaved air and carbogen (97% O2 , 3% CO2 ) breathing was employed in nine rabbits. Parametrical R2 /R2 '/R2 * maps were computed and average R2 /R2 '/R2 * values were measured in regions of interest in the renal medulla and cortex. Bland-Altman plots showed good agreement between the proposed method and reference standards of multi-echo spin echo and multi-echo gradient echo sequences. Renal R2 , R2 ' and R2 * decreased significantly from 16.2 ± 4.4 s-1 , 9.8 ± 5.2 s-1 and 25.9 ± 5.0 s-1 to 14.9 ± 4.4 s-1 (p < 0.05), 8.5 ± 4.1 s-1 (p < 0.05) and 23.4 ± 4.8 s-1 (p < 0.05) in the cortex when switching the gas mixture from room air to carbogen. In the renal medulla, R2 , R2 ' and R2 * also decreased significantly from 12.9 ± 4.7 s-1 , 15.1 ± 5.8 s-1 and 27.9 ± 5.3 s-1 to 11.8 ± 4.5 s-1 (p < 0.05), 14.2 ± 4.2 s-1 (p < 0.05) and 25.8 ± 5.1 s-1 (p < 0.05). No statistically significant differences in relative R2 , R2 ' and R2 * changes were observed between the cortex and medulla (p = 0.72 for R2 , p = 0.39 for R2 ' and p = 0.61 for R2 *). The psMASE-ME method for dynamic renal R2 /R2 '/R2 * measurements, together with the respiratory challenge, has potential use in the evaluation of renal oxygenation in many renal diseases.

Dynamic oxygen challenge evaluated by NMR T1 and T2*--insights into tumor oxygenation.

There is intense interest in developing non-invasive prognostic biomarkers of tumor response to therapy, particularly with regard to hypoxia. It has been suggested that oxygen sensitive MRI, notably blood oxygen level-dependent (BOLD) and tissue oxygen level-dependent (TOLD) contrast, may provide relevant measurements. This study examined the feasibility of interleaved T2*- and T1-weighted oxygen sensitive MRI, as well as R2* and R1 maps, of rat tumors to assess the relative sensitivity to changes in oxygenation. Investigations used cohorts of Dunning prostate R3327-AT1 and R3327-HI tumors, which are reported to exhibit distinct size-dependent levels of hypoxia and response to hyperoxic gas breathing. Proton MRI R1 and R2* maps were obtained for tumors of anesthetized rats (isoflurane/air) at 4.7 T. Then, interleaved gradient echo T2*- and T1-weighted images were acquired during air breathing and a 10 min challenge with carbogen (95% O2 -5% CO2). Signals were stable during air breathing, and each type of tumor showed a distinct signal response to carbogen. T2* (BOLD) response preceded T1 (TOLD) responses, as expected. Smaller HI tumors (reported to be well oxygenated) showed the largest BOLD and TOLD responses. Larger AT1 tumors (reported to be hypoxic and resist modulation by gas breathing) showed the smallest response. There was a strong correlation between BOLD and TOLD signal responses, but ΔR2* and ΔR1 were only correlated for the HI tumors. The magnitude of BOLD and TOLD signal responses to carbogen breathing reflected expected hypoxic fractions and oxygen dynamics, suggesting potential value of this test as a prognostic biomarker of tumor hypoxia.

Influence of carbon dioxide insufflation of the neck on intraocular pressure during robot-assisted endoscopic thyroidectomy: a comparison with open thyroidectomy.

BACKGROUND: Increased intraocular pressure (IOP) during surgery can result in serious ophthalmic complications. We hypothesized that carbon dioxide (CO2) insufflation of the neck during endoscopic thyroidectomy would constrict the jugular veins mechanically, causing elevated venous pressure and thus elevated IOP. We compared IOP changes at each step of open thyroidectomy (OT) versus robot-assisted endoscopic thyroidectomy (RET) METHODS: Perioperatively, IOP was measured at six time points in patients undergoing OT (n = 18) or RET with CO2 insufflation (n = 19). Anesthesia, ventilatory strategy, intravenous infusions, and surgical positioning were standardized RESULTS: In both groups, induction of anesthesia reduced IOP, but surgical positioning with the neck in extension had no effect on IOP. In the OT group, IOP remained unchanged during anesthesia. In the RET group, CO2 insufflation significantly increased IOP to an average of 3.6 ± 3.0 mmHg higher than the previous measurement (P < 0.001), and this IOP increase persisted immediately before gas deflation. These elevated IOP values during CO2 insufflation in the RET group were significantly higher than those at corresponding time points in the OT group. However, these elevated IOP values were similar to the pre-anesthetic baseline IOP CONCLUSION: CO2 insufflation of the neck at pressure of 6 mmHg increased the IOP significantly compared with open thyroidectomy. However, this increase in IOP could be balanced by an anesthetic-induced IOP-lowering effect, thereby having no clinical significance in patients with normal IOP undergoing robot-assisted endoscopic thyroidectomy.

Air-water fluxes of N2O and CH4 during microalgae (Staurosira sp.) cultivation in an open raceway pond.

The industrial-scale production of biofuels from cultivated microalgae has gained considerable interest in the last several decades. While the climate benefits of microalgae cultivation that result from the capture of atmospheric CO(2) are known, the counteracting effect from the potential emission of other greenhouse gases has not been well quantified. Here, we report the results of a study conducted at an industrial pilot facility in Hawaii to determine the air-water fluxes of N(2)O and CH(4) from open raceway ponds used to grow the marine diatom Staurosira sp. as a feedstock for biofuel. Dissolved O(2), CH(4), and N(2)O concentrations were measured over a 24 h cycle. During this time, four SF(6) tracer release experiments were conducted to quantify gas transfer velocities in the ponds, and these were then used to calculate air-water fluxes. Our results show that pond waters were consistently supersaturated with CH(4) (up to 725%) resulting in an average emission of 19.9 ± 5.6 µmol CH(4) m(-2) d(-1). Upon NO(3)(-) depletion, the pond shifted from being a source to being a sink of N(2)O, with an overall net uptake during the experimental period of 3.4 ± 3.5 µmol N(2)O m(-2) d(-1). The air-water fluxes of N(2)O and CH(4) expressed as CO(2) equivalents of global warming potential were 2 orders of magnitude smaller than the overall CO(2) uptake by the microalgae.

A simple method to clamp end-tidal carbon dioxide during rest and exercise.

Carbon dioxide regulates ventilation and cerebral blood flow during exercise. There are significant limitations in breathing systems designed to control end-tidal gas concentrations when used during high-intensity exercise. We designed a simple, inexpensive breathing system which controls end-tidal carbon dioxide (PET CO2) during exercise from rest to peak work capacity (W(max)). The system is operated by an investigator who, in response to breath-by-breath PET CO2, titrates flow of a 10 % CO(2), 21 % O(2) mixture into an open-ended 5-L inspiratory reservoir. To demonstrate system efficacy, nine fit male subjects performed two maximal, incremental exercise tests (25 W min(-1) ramp) on a cycle ergometer: a poikilocapnic control trial in which PET CO2 varied with work intensity, and an experimental trial, in which we planned to clamp PET CO2 at 50 mmHg. With our breathing system, we maintained PET CO2 at 51 ± 2 mmHg throughout exercise (rest, 50 ± 2; W(max), 52 ± 5 mmHg; mean ± SD) despite large changes in ventilation (range 27-65 at rest, 134-185 L min(-1) BTPS at W (max)) and carbon dioxide production (range 0.3-0.7 at rest, 4.5-5.5 L min(-1) at W (max)). This simple, inexpensive system achieves PET CO2 control at rest and throughout exercise.

Changes in end-tidal carbon dioxide due to gastric perforation during pneumoperitoneum in the rat.

BACKGROUND: Carbon dioxide is the most widely used gas to establish pneumoperitoneum during laparoscopic surgery. Gastrointestinal trauma may occur during the peritoneal insufflation or during the operative phase itself. Early diagnosis of these injuries is critical. OBJECTIVES: To assess changes in end-tidal carbon dioxide (ETCO2) following gastric perforation during pneumoperitoneum in the rat. METHODS: Wistar rats were anesthetized, tracheotomized and mechanically ventilated with fixed minute volume. Each animal underwent a 1 cm abdominal longitudinal incision. A 0.3 x 0.3 cm cross-incision of the stomach was performed in the perforation group but not in the controls (n = 10/group) and the abdomen was closed in both groups. After stabilization, CO2-induced pneumoperitoneum was established at 0, 5, 8 and 12 mmHg for 20 min periods consecutively, each followed by complete pressure relief for 5 min. RESULTS: Ventilatory pressure increased in both groups when pneumoperitoneal pressure 5 mmHg was applied, but more so in the perforated stomach group (P = 0.003). ETCO2 increased in both groups during the experiment, but less so in the perforated group (P = 0.04). It then returned to near baseline values during pressure annulation in all perforated animals but only following the 0 and 5 mmHg periods in the controls. CONCLUSIONS: When subjected to pneumoperitoneum, ETCO2 was lower in rats with a perforated stomach than in those with an intact stomach. An abrupt decrease in ETCO2 during laparoscopy may signal gastric perforation.

The cerebrovascular response to carbon dioxide in humans.

Carbon dioxide (CO2) increases cerebral blood flow and arterial blood pressure. Cerebral blood flow increases not only due to the vasodilating effect of CO2 but also because of the increased perfusion pressure after autoregulation is exhausted. Our objective was to measure the responses of both middle cerebral artery velocity (MCAv) and mean arterial blood pressure (MAP) to CO2 in human subjects using Duffin-type isoxic rebreathing tests. Comparisons of isoxic hyperoxic with isoxic hypoxic tests enabled the effect of oxygen tension to be determined. During rebreathing the MCAv response to CO2 was sigmoidal below a discernible threshold CO2 tension, increasing from a hypocapnic minimum to a hypercapnic maximum. In most subjects this threshold corresponded with the CO2 tension at which MAP began to increase. Above this threshold both MCAv and MAP increased linearly with CO2 tension. The sigmoidal MCAv response was centred at a CO2 tension close to normal resting values (overall mean 36 mmHg). While hypoxia increased the hypercapnic maximum percentage increase in MCAv with CO2 (overall means from76.5 to 108%) it did not affect other sigmoid parameters. Hypoxia also did not alter the supra-threshold MCAv and MAP responses to CO2 (overall mean slopes 5.5% mmHg⁻¹ and 2.1 mmHg mmHg⁻¹, respectively), but did reduce the threshold (overall means from 51.5 to 46.8 mmHg). We concluded that in the MCAv response range below the threshold for the increase of MAP with CO2, the MCAv measurement reflects vascular reactivity to CO2 alone at a constant MAP.

Physiological changes in transperitoneal versus retroperitoneal laparoscopy in children: a prospective analysis.

PURPOSE: The choice of minimally invasive surgical approaches in pediatric urology is largely influenced by surgeon preference and experience. Little is known about the differences in physiological variables that might objectively influence the choice of surgical approach. We compared the cerebral and systemic hemodynamic effects of transperitoneal vs retroperitoneal CO(2) insufflation in children. MATERIALS AND METHODS: After receiving ethical review board approval and written parental consent 36 pediatric patients undergoing transperitoneal (18) or retroperitoneal (18) laparoscopic surgery were enrolled in this study. A standardized anesthetic technique of isoflurane 1 MAC and remifentanil 0.2 mcg/kg per minute was used. Measured parameters included end tidal CO(2), middle cerebral artery blood flow velocity, heart rate and noninvasive mean arterial blood pressure. Transcranial Doppler ultrasound was used to measure middle cerebral artery blood flow velocity. Data were collected before, during and after CO(2) insufflation to 12 mm Hg pneumoperitoneum at regular intervals, including every minute for 10 minutes and every 2 minutes thereafter. Within group analysis was done using repeated measures ANOVA. Nonlinear regression analysis was used to determine the best fit and the relationship of each variable with time with p <0.05 considered significant. RESULTS: Patient age and weight were comparable in the 2 groups. Transperitoneal CO(2) insufflation resulted in a rapid parallel increase in middle cerebral artery blood flow velocity, mean arterial pressure and end tidal CO(2) during the first 8 minutes of pneumoperitoneum (p <0.05). Despite a continued increase in end tidal CO(2) thereafter middle cerebral artery blood flow velocity and mean arterial pressure attained a plateau within the first 8 minutes (p <0.05). In contrast, middle cerebral artery blood flow velocity and end tidal CO(2) increased progressively throughout the retroperitoneal CO(2) insufflation period (p <0.01). CONCLUSIONS: Cerebral blood flow velocity and end tidal CO(2) seem to increase progressively and gradually during retroperitoneal laparoscopy, in contrast to the more rapid increase and plateau effect during transperitoneal laparoscopy. Presumably the smaller absorptive surface in the retroperitoneal space explains this physiological difference.

Enhancing gas adsorption and separation capacity through ligand functionalization of microporous metal-organic framework structures.

Hydroxyl- and amino- functionalized [Zn(BDC)(TED)(0.5)]·2DMF·0.2H(2)O leads to two new structures, [Zn(BDC-OH)(TED)(0.5)]·1.5DMF·0.3H(2)O and [Zn(BDC-NH(2))(TED)(0.5)]·xDMF·yH(2)O (BDC=terephthalic acid, TED=triethylenediamine, BDC-OH=2-hydroxylterephthalic acid, BDC-NH(2)=2-aminoterephthalic acid). Single-crystal X-ray diffraction and powder X-ray diffraction studies confirmed that the structures of both functionalized compounds are very similar to that of their parent structure. Compound [Zn(BDC)(TED)(0.5)]·2DMF·0.2H(2)O can be considered a 3D porous structure with three interlacing 1D channels, whereas both [Zn(BDC-OH)(TED)(0.5)]·1.5DMF·0.3H(2)O and [Zn(BDC-NH(2))(TED)(0.5)]·xDMF·yH(2)O contain only 1D open channels as a result of functionalization of the BDC ligand by the OH and NH(2) groups. A notable decrease in surface area and pore size is thus observed in both compounds. Consequently, [Zn(BDC)(TED)(0.5)]·2DMF·0.2H(2)O takes up the highest amount of H(2) at low temperatures. Interestingly, however, both [Zn(BDC-OH)(TED)(0.5)]·1.5DMF·0.3H(2)O and [Zn(BDC-NH(2))(TED)(0.5)]·xDMF·yH(2)O show significant enhancement in CO(2) uptake at room temperature, suggesting that the strong interactions between CO(2) and the functionalized ligands, indicating that surface chemistry, rather than porosity, plays a more important role in CO(2) adsorption. A comparison of single-component CO(2), CH(4), CO, N(2), and O(2) adsorption isotherms demonstrates that the adsorption selectivity of CO(2) over other small gases is considerably enhanced through functionalization of the frameworks. Infrared absorption spectroscopic measurements and theoretical calculations are also carried out to assess the effect of functional groups on CO(2) and H(2) adsorption potentials.

Carbon dioxide insufflation compared with air insufflation in double-balloon enteroscopy: a prospective, randomized, double-blind trial.

BACKGROUND: Few studies have evaluated the degree of pain, the amount of retained gas, and the safety of carbon dioxide (CO(2)) insufflation in patients undergoing double-balloon enteroscopy (DBE). OBJECTIVE: To clarify the usefulness and safety of CO(2) insufflation during DBE. DESIGN: Single-center, prospective, randomized, double-blind, controlled trial. SETTING: University hospital. PATIENTS: Forty eligible patients with small-bowel disease for whom DBE was indicated were randomized to a CO(2) insufflation (CO(2)) group or an air insufflation (air) group by means of sealed envelopes. INTERVENTION: DBE with insufflation of CO(2) or air. MAIN OUTCOME MEASUREMENTS: Efficacy evaluation was based on the degree of pain as assessed by use of a visual analog scale (VAS) and the amount of residual gas retention within the small and large bowels on radiography. The safety of CO(2) insufflation was evaluated by arterial blood gas analysis. RESULTS: Significantly fewer patients in the CO(2) group had severe pain of ≥ 50 mm on the VAS during DBE than in the air group (P = .02). Significantly less gas was retained in the small bowel just after and at 3 hours after DBE in the CO(2) group than in the air group (P = .003, P = .01, respectively). There was significantly less residual gas retention in the large bowel at 3 hours after DBE in the CO(2) group than in the air group (P = .02). There was no significant difference in pre-DBE and post-DBE partial pressure of oxygen in the blood (PaO(2)) and partial pressure of carbon dioxide in the blood (PaCO(2)) between groups. LIMITATIONS: Small sample size. CONCLUSION: CO(2) insufflation is a safe and useful procedure when performed during DBE.

[Carbon dioxide baths: state of the art].

Modern concepts of the mechanism of therapeutic action of carbon dioxide are reviewed with special reference to its effects on the patients with different pathologies undergoing treatment with the use of carbon dioxide baths. Further prospects for practical application of this method are discussed.

Comparison of normal tissue R1 and R*2 modulation by oxygen and carbogen.

Magnetic resonance imaging has shown promise for evaluating tissue oxygenation. In this study differences in the tissue longitudinal relaxation rate (R(1)) and effective transverse relaxation rate (R(*)(2)), induced by inhalation of pure oxygen and carbogen, were evaluated in 10 healthy subjects. Significant reductions in R(1) were demonstrated following both oxygen and carbogen inhalation in the spleen (both P < 0.001), liver (P = 0.002 air vs. oxygen; P = 0.001 air vs. carbogen), skeletal muscle (both P < 0.001), and renal cortex (P = 0.005 air vs. oxygen; P = 0.008 air vs. carbogen). No significant change in R(*)(2) occurred following pure oxygen in any organ. However, a significant increase in R(*)(2) was observed in the spleen (P < 0.001), liver (P = 0.001), skeletal muscle (P = 0.026), and renal cortex (P = 0.001) following carbogen inhalation, an opposite effect to that observed in many studies of tumor pathophysiology. Changes in R(1) and R(*)(2) were independent of the gas administration order in the spleen and skeletal muscle. These findings suggest that the R(1) and R(*)(2) responses to hyperoxic gases are independent biomarkers of oxygen physiology.

CO2 chemosensing in rat oesophagus.

BACKGROUND: Acid in the oesophageal lumen is often sensed as heartburn. It was hypothesised that luminal CO(2), a permeant gas, rather than H(+), permeates through the epithelium, and is converted to H(+), producing an afferent neural signal by activating chemosensors. METHODS: The rat lower oesophageal mucosa was superfused with pH 7.0 buffer, and pH 1.0 or pH 6.4 high CO(2) (P(CO2) = 260 Torr) solutions with or without the cell-permeant carbonic anhydrase (CA) inhibitor methazolamide (MTZ, 1 mM), the cell-impermeant CA inhibitor benzolamide (BNZ, 0.1 mM), the transient receptor potential vanilloid 1 (TRPV1) antagonist capsazepine (CPZ, 0.5 mM) or the acid-sensing ion channel (ASIC) inhibitor amiloride (0.1 mM). Interstitial pH (pH(int)) was measured with 5',6'-carboxyfluorescein (5 mg/kg intravenously) loaded into the interstitial space, and blood flow was measured with laser-Doppler. RESULTS: Perfusion of a high CO(2) solution induced hyperaemia without changing pH(int), mimicking the effect of pH 1.0 perfusion. Perfused MTZ, BNZ, CPZ and amiloride all inhibited CO(2)-induced hyperaemia. CA XIV was expressed in the prickle cells, with CA XII in the basal cells. TRPV1 was expressed in the stratum granulosum and in the muscularis mucosa, whereas all ASICs were expressed in the prickle cells, with ASIC3 additionally in the muscularis mucosa. CONCLUSIONS: The response to CO(2) perfusion suggests that CO(2) diffuses through the stratum epithelium, interacting with TRPV1 and ASICs in the epithelium or in the submucosa. Inhibition of the hyperaemic response to luminal CO(2) by CA, TRPV1 and ASIC inhibitors implicates CA and these chemosensors in transduction of the luminal acid signal. Transepithelial CO(2) permeation may explain how luminal H(+) equivalents can rapidly be transduced into hyperaemia, and the sensation of heartburn.

The Effect of Carbogen Breathing on 18F-FDG Uptake in Non-Small-Cell Lung Cancer.

It has been reported that 18F-FDG uptake is higher in hypoxic cancer cells than in well-oxygenated cells. We demonstrated that 18F-FDG uptake in lung cancer would be affected by high concentration oxygen breathing. Methods. Overnight fasted non-small-cell lung cancer A549 subcutaneous (s.c.) xenografts bearing mice (n = 10) underwent 18F-FDG micro-PET scans, animals breathed room air on day 1, and same animals breathed carbogen (95% O2 + 5% CO2) on the subsequent day. In separated studies, autoradiography and immunohistochemical staining visualization of frozen section of A549 s.c. tumors were applied, and to compare between carbogen-breathing mice and those with air breathing, a combination of 18F-FDG and hypoxia marker pimonidazole was injected 1 h before animal sacrifice, and 18F-FDG accumulation was compared with pimonidazole binding and glucose transporter 1 (GLUT-1) expression. Results. PET studies revealed that tumor 18F-FDG uptake was significantly decreased in carbogen-breathing mice than those with air breathing (P < 0.05). Ex vivo studies confirmed that carbogen breathing significantly decreased hypoxic fraction detected by pimonidazole staining, referring to GLUT-1 expression, and significantly decreased 18F-FDG accumulation in tumors. Conclusions. High concentration of O2 breathing during 18F-FDG uptake phase significantly decreases 18F-FDG uptake in non-small-cell lung cancer A549 xenografts growing in mice.